The present invention relates to a system for monitoring the pressure of tires on a vehicle, particularly a commercial vehicle such as a tractor trailer. The invention is concerned with a magnetic detection technique and employs a rotating sensor unit cooperatively associated with a non-rotating detector unit.
There are a number of prior art systems for detecting the pressure condition of vehicle tires. See for example, U.S. Pat. Nos. 3,831,161; 3,614,732; 3,665,387; 3,858,174; and 3,602,884. Of these known systems there are certain disadvantages associated therewith and it is one of the objects of this invention to provide an improved system which overcomes many of these disadvantages. For example, a system of the type shown in U.S. Pat. No. 3,602,884 requires modification of the tire rim. Also, this system mounts the detection components outside of the wheel assembly and essentially unprotected. Other prior art systems are rather complicated in construction and still other systems are not readily adaptable to any existing diagnosis system presently used with the vehicle. The system of the present invention is particularly useful with a diagnosis system of the type shown in U.S. Pat. No. 3,975,708.
Accordingly, one object of the present invention is to provide an improved system for monitoring vehicle tire pressure employing an improved form of magnetic coupling detection. In accordance with the invention when tire pressure is sufficiently low, a resonant condition exists, which condition is inductively coupled to amplitude detection means.
Another object of the present invention is to provide a tire pressure monitoring system that includes a sensor unit and a detector unit physically unattached to the sensor unit and wherein both units are mounted so as to be enclosed and thus protected from dirt, grease, etc. In accordance with the invention the sensor unit is secured to the inner surface of the tire rim in the space provided between the rim and the tire itself. The detector unit is secured to the brake shoe or the inner surface of the backing plate so as to be substantially enclosed between the backing plate and the brake drum.
A further object of the present invention is to provide a tire pressure monitoring system that requires substantially no alteration of the existing wheel system of the vehicle. In accordance with the invention, rather than providing passages or the like through the rim for receiving a transducer, the sensor unit of this invention secured to the inner surface of the rim without requiring any alteration to the rim.
Still another object of the present invention is to provide an improved tire pressure monitoring system that is readily adaptable for use with an existing diagnosis system presently in the vehicle.